Will drum-playing bacteria be the next big thing in fighting antibacterial resistance?

Zen philosophers may ponder the sound of one hand clapping, but researchers have recorded the sound of one bacterium playing the drum.

What’s more, this acoustic enquiry may provide another tool in the struggle against antibiotic resistance.

According to the World Health Organisation fact sheet on the subject: “Antibiotic resistance is one of the biggest threats to global health, food security, and development today.

“Bacteria, not humans or animals, become antibiotic-resistant. These bacteria may infect humans and animals, and the infections they cause are harder to treat than those caused by non-resistant bacteria.”

To determine whether bacteria are becoming resistant to an antibiotic, researchers need to know whether the drugs can efficiently kill off a bacterium.

By recording the sounds of a bacterium playing a microscopic drum, researchers from TU Delft, in the Netherlands, led by Dr Farbod Alijani were able to efficiently check the health of bacterium using sound. Their work was published yesterday in the journal Nature Nanotechnology.

So, how can a bacterium bang a drum?

The researchers were originally investigating the drum, which is a form of carbon called graphene, not the drummer.

“Graphene is a form of carbon consisting of a single layer of atoms and is also known as the wonder material,” says Alijani. “It’s very strong with nice electrical and mechanical properties, and it’s also extremely sensitive to external forces.”

To test this sensitivity the team decided to see what would happen if the graphene encountered a single biological object… a single E. coli bacterium.

“What we saw was striking!” says Alijani. “When a single bacterium adheres to the surface of a graphene drum, it generates random oscillations with amplitudes as low as a few nanometers that we could detect. We could hear the sound of a single bacterium.”

The majority of the oscillations were being driven by the E. coli’s flagella. Flagella are the tail or hair-like structures of the cell surface that wiggle and twist, propelling the cell.

“To understand how tiny these flagellar beats on graphene are, it’s worth saying that they are at least 10 billion times smaller than a boxer’s punch when reaching a punch bag,” Alijani says. “Yet, these nanoscale beats can be converted to soundtracks and listened to – and how cool is that?”

But how can bacteria that have caught the beat be used to fight disease?

This research is still early days, but Alijani and his team are hopeful that it could be used to identify bacteria that has become resistant to antibiotics.

When a resistant bacterium was exposed to antibiotics on the graphene drum, its oscillations continued at the same level – the beat did not stop.

But when bacteria were susceptible to a drug, the rhythm would die along with the bacterium. After antibiotic exposure these dying bacteria would beat out a song that was operatic in length if not in scale. The vibrations they created would slowly decrease over the span of one or two hours until eventually they ceased.

The wonder of this technology is that it can detect antibiotic resistance at the scale of a single cell.

“For the future, we aim at optimising our single-cell graphene antibiotic sensitivity platform and validate it against a variety of pathogenic samples,” Alijani says. “So that eventually it can be used as an effective diagnostic toolkit for fast detection of antibiotic resistance in clinical practice. “This would be an invaluable tool in the fight against antibiotic resistance, an ever- increasing threat to human health around the world.”

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